NOTE: This has changed to a minimum of 62 degrees, regardless of the outdoor temperature.

January and February obviously have the lowest Average Daily Temperatures, which means they will have the highest number of HDDs. One important takeaway from this chart is how much heating seasons can vary year to year. For example, the Average Daily Temperature was 24⁰F in February 2015, 37⁰F in February 2016 and 41⁰F in February 2017. That’s a 17⁰F swing in only 2 years! It’s important that your boiler system is able to take advantage of the milder heating seasons so that you’re not over paying for fuel.